1. Field
One embodiment of the present invention relates to a printed wiring board assembly having components, such as ball grid arrays (BGA) and the like, mounted on both surfaces of the board.
2. Description of the Related Art
An electronic apparatus, such as a personal computer, is equipped with a printed wiring board on which various semiconductor circuit components are mounted to configure desired functional circuits. The semiconductor circuit component includes a CPU chip, a CPU family chip, and an IO chip. Since a BGA component is large in size and produces much heat, and since the BGA component is bonded to a printed wiring board by means of solder balls arranged in the form of an array on its package back surface, when the printed wiring board is placed in a casing as a circuit board, the printed wiring board will warp due to the thermal deformation or external stress. In the event of such a warp, the solder-mounting surface of the BGA component will be subjected to excessive stress, resulting in failure of the normal bonded condition of the bonded portions. In order to avoid such a disadvantage, a technique has been proposed by which the BGA component solder-mounting surface is reinforced by means of a back plate provided on the other surface (see JP-A No. 2006-210852: KOKAI).
With such a printed wiring board on which a large sized BGA component producing much heat is mounted, when BGA components are each to be mounted on a respective one of the surfaces of the board so that they overlap each other, the solder-mounting surface of the BGA component cannot be reinforced by a back plate with sufficient strength. This problem will also occur when a BGA component is mounted on one surface of a printed wiring board and another circuit component is mounted on the other surface so that they overlap each other.
As described above, when BGA components are each mounted on respective surfaces of a printed wiring board so that they overlap each other, there arises a problem that a back plate to reinforce the BGA component solder-mounting surface cannot be provided. The same problem also arises in a case where a BGA component is mounted on one surface of a printed wiring board and another circuit component is mounted on the other surface so that they overlap each other.
According to one aspect of the present invention, there is provided a printed wiring board assembly comprising: a printed wiring board; a first component mounting portion provided on a first surface of the printed wiring board; a second component mounting portion provided on a second surface of the printed wiring board so that it overlaps the first component mounting portion; a BGA component mounted on the first component mounting portion; a circuit component mounted on the second component mounting portion; and a supplementary component which is provided on the second surface of the printed wiring board and functions as a heat-sink portion to remove heat produced from the circuit component and as a reinforcement portion to reinforce the first component mounting portion.